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John Becker - earth resistivity meter for caves and galleries in chalk- ?

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  • John Becker - earth resistivity meter for caves and galleries in chalk- ?

    Hello,

    This is my first post, so let me tell you first that I was really glad to find such a forum, where I coud find a lot of valuable informations

    Going to my point :

    My family lives in what was an old abbaye, almost totally destroyed today, but where there might still be some caves, and galleries.

    There is actualy one cave that goes 10 meters down, surely a quarry for the chalk, that became after a cave. In that cave they started to dig two galleries, but those go nowhere after a few meters.

    A couple of years ago, a hole appeared in the soil, 30 meters far from the entrance of the first cave, in the middle of nowhere (it does not correspond to anything in particular on the few old maps we have).
    It is a squared hole, 1 meter wide, 1 meter long, and maybe 1.5 meters depth. Actualy the hole might have been obstructed with soil.

    I wanted to dig in it, as I thought it might be some aeration for a gallery, but my family did not want me to touch anything. (too dangerous they said)

    Also, an other story : there's high chance that there was a crypt under the church (some old texts talk about it), but we don't know if it was destroyed or if it still there.


    So here I am today, trying to figure out how to see beneath the soil, and see if there's a crypt, some caves, some galleries, or nothing at all.


    I want to construct the resistivity meter that John Becker wrote about in 2003. I have the Pdf, and I understood the principle. I bought the electronics part, I think that I might be able to build it, and learn how to use it.

    But I have some wonders that came after buying everything :
    - I bought some capacitor as said in the pdf : 1 and 10 microF, but rather than 16V I could only found 50V. Does that matters ? Is it just because the technology improved and that we have 50V rather than 16V today, or is it essential to get 16V ?
    - The soil I am trying to explore is mostly made of chalk. Is it a problem to detect large voids ? I am afraid that the resistivity of chalk won't allow me to see anything...

    - I've seen many time that people use a resistivity meter with a commutator, and a large amount of electrodes , so that the capture takes far less time (rather than having to connecte/disconnect wires for each measure). What do I need to build such a system, and is there any ressources out there ?


    Ok tell me what you think

    Thank you

    -Thomas

  • #2
    Originally posted by ophiucus View Post
    ...
    But I have some wonders that came after buying everything :
    - I bought some capacitor as said in the pdf : 1 and 10 microF, but rather than 16V I could only found 50V. Does that matters ? Is it just because the technology improved and that we have 50V rather than 16V today, or is it essential to get 16V ?
    - The soil I am trying to explore is mostly made of chalk. Is it a problem to detect large voids ? I am afraid that the resistivity of chalk won't allow me to see anything...
    - I've seen many time that people use a resistivity meter with a commutator, and a large amount of electrodes , so that the capture takes far less time (rather than having to connecte/disconnect wires for each measure). What do I need to build such a system, and is there any ressources out there ?
    ...Thomas
    - No it is not essential to get 16v. Follow the voltage values at those caps paths (on schematic) and try always to put caps with a bit higher voltage rate. Your 50V caps will do just fine.
    - Depends of your surveying strategy. It is doable. If you take small "reference" measurements at that particular soil; later you will follow differences and variations relating to those references.
    - Yes; you've seen 2D Profile probe setup. Not directly applicable to Becker's setup... but with extension of mentioned commutator maybe it is... can't tell for sure.

    I made Becker's ERM several years ago. It's quite alright. Yet... EPE's Resistivity logger is more modern and better. I had a bit of problems with batteries than. Actually it needed 36 volts!! (+/-18V)
    So i used 6x6V gell cell accu's setup! (or two 12V+ two 6V can be used too) .Man it was uncomfortable!
    Later i had problems to recharge them, so i figured out pretty funny mechanical multiple switching to achieve "working" and "recharging" modes for those accu's, in manner to avoid unpacking them from "power" box!
    Now days that can be solved with different approach; with use of DC/DC and accu with lower voltage.

    Comment


    • #3
      Thank you for your answer Ivconic

      EPE's Resistivity logger is more modern and better
      What ? I thought that John Becker's logger was the "EPE's resistivity logger" people are talking about...So there is an other one ? Where can I find the "new" one ? And is it better ? Simpler ? More efficient ?

      For the battery, that's good that you tell me as I was not sure what to use yet. So what would you recommend me ? Any particular brand or model ?

      Thanks for your feedback again, as I was starting to freak out that it might not work after all..

      Comment


      • #4
        Originally posted by ophiucus View Post
        Thank you for your answer Ivconic


        What ? I thought that John Becker's logger was the "EPE's resistivity logger" people are talking about...So there is an other one ? Where can I find the "new" one ? And is it better ? Simpler ? More efficient ?

        For the battery, that's good that you tell me as I was not sure what to use yet. So what would you recommend me ? Any particular brand or model ?

        Thanks for your feedback again, as I was starting to freak out that it might not work after all..

        Sheesh! I am sorry! Misunderstanding!
        Must be that i gone pretty senile lately!
        Yes, ERM you are talking about is the better one! Keep on making it, don't worry!
        I mixed it up with Robert Beck's older design, EPE January 1997!!
        Forget what i told you about accu's!
        No such problem at Becker's design!
        Just use 9v battery and in case you want longer "life": use 12V gel cell accu and 7809 voltage regulator after it.
        The rest i told you is alright.

        Comment


        • #5
          In addition, instead pretty obscure PC software EPE offered for use with ERM; you can use Snuffler, which is much much better.
          Recently new version appeared on author's page.

          Comment


          • #6
            Ok that's great
            Thank you very much ! Really appreciate your help

            I'll try to build the system and tell you if I found anything interesting in the soil

            Comment

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